Conversion of reversible phase a. c. signal to reversible polarity d. c. signal



J. GRILLO CONVERSION OF REVERSIBLE PHASE A. C. SIGNAL April 3, 1956 TO REVERSIBLE POLARITY D. C. SIGNAL Filed July 24, 1952 United States Patent O CONVERSION OF REVERSIBLE PHASE A. C. T; REVERSIBLE POLARIIY D. C. N

Joseph Grillo, New York, N. Y., assignor to Ward Leonard Electric Company, a corporation of New York Application July 24, 1952, Serial No. 300,685

5 Claims. (Cl. 340-178) Another object of the invention is to provide an electrical circuit that has a direct voltage output signal directly proportional to the input signal in magnitude and reversing in polarity with reversal in phase of the input signal.

Another object of the invention is to provide a conversion circuit with a single ended amplifier.

Other and further objects will be apparent from the following description taken in connection with accompanying drawings;

In the embodiment shown and described theinput circuit receives an alternating control signal from the control circuit 11 and an alternating reference voltage from the alternating source 12. The source 12 also supplies the control circuit 11 with an alternating signal so that the output of the control circuit and the alternating source are of the same frequency. The control circuit 11 varies the alternating signal in amplitude and may shift the phase of the reference signal from an in phase relation with the reference voltage to a 180 degree phase relation with the reference voltage. When in either phase relation the phase remains constant.

The control signal with these amplitude variations and phase reversal is added to the alternating voltage in the input circuit and the resultant is rectified to a direct current signal variable between a maximum and minimum voltage of the same polarity. This direct current output signal is amplified in the two stage amplifier 14 and impressed on the ring modulator 16. In the ring modulator the amplified signal is combined with a direct reference voltage from the reference circuit 15 to produce an'ou'tput signal variable between a maximum positive value and a minimum negative value. The output signal is used to control the load circuits connected to 39 and 40.

The output of the amplifier is fed to the ring demodulator 16 which subtracts out that portion of the ampli fied direct current which originated from the alternating reference source 12. This leaves only the amplified direct current, which originated from the alternating signal from the control circuit 11. This signal output appears across load resistors 39 and 40 and is proportional to the magnitude of the signal. The signal output will have a positive or negative polarity dependent upon whether a 180 phase reversal has taken place in the signal. Auxiliary supply circuits are provided to supply power to the amplifier and ring demodulator. Anode supply transformer 34, and bias supply circuit 29 provide the amplitier with external power, and the demodulator supply 15 provides the ring demodulator with reference power.

The control circuit 11 and the alternating reference 2,740,950 Patented Apr. 3, 1956 circuit 12 provides the input circuit 10 with an alternating signal and reference. The alternating signal may vary in magnitude and may reverse phase by such as the signal which is commonly derived from the output of a synchro control transformer. The phase of the signal must remain relatively constant excepting for the 180 reversals. It is required that the signal and reference circuits be powered from a common alternating source in such a manner that the phase relation of the two circuits is always fixed excepting for phase reversals of 180". If a permanent phase shift is encountered in the signal circuit, a corresponding phase shift must be introduced into the reference.

Considering the conversion circuit in greater detail the alternating control signal and the alternating reference voltage are combined in the secondaries of transformers 18 and 19 of the input circuit 10. The primary windings 18a, 19a are connected to the control circuit 11 and the source 12 respectively. The secondary windings 18b and 19b are connected in series and combine the signal with the reference voltage. The alternating reference or source voltage has an amplitude greater than the largest amplitude of the control signal and may be compensated for any phase shift through the signal source. The bridge rectifier 20 is connected across the windings 18b, 19b and rectifies the net signal to produce a direct voltage between minimum values of the same polarity. The output of the rectifier is connected to the input of the amplifier 14 through the filter 21.

The primary 18a of the signal transformer and the primary 19b of the reference transformer are isolated providing signal and reference isolation. The secondary 18b of the signal transformer and the secondary 19b of the reference transformer are connected in series. This provides electrical mixing of the output voltages from the signal and reference circuits. The turns of the reference transformer 19 are so apportioned that the reference voltage will always be greater in magnitude than the maximum possible signal voltage. In this manner the signal voltage may be varied in magnitude or by 180 phase reversal and yet will always add or subtract from the larger reference voltage without reversal of the phase of the net voltage. This net voltage from the signal and reference circuits is rectified to a direct current signal by rectifier 20, the direct current output of which is filtered by the L section, choke input, filter 21. This direct 1 current signal will be variable between a maximum and minimum voltage, but will never reverse polarity. The mean of these variations will correspond to an input signal of 0, while signals in phase with the reference will result in direct currents above the mean, and those shifted in phase 180 will result in currents below the mean. The signal has now been converted to avariable direct current which is directly related to the nature of the input signal.

The magnetic amplifier 14 has two stages of amplification with a feedback from the output of the amplifier to the first stage. The response of the amplifier is very linear over the operating range which is from an input voltage equal to the difference of the control voltage and the reference voltage to an input voltage equal to the sum of the two voltages. The. first stage comprises saturaole reactors 22, 22' with a bridge rectifier 23 in the output and the second stage comprises a saturable reactor 25 with a bridge rectifier 26. The saturable reactors may be of the conventional three legged shell type with the bias and control windings on the center leg and the-anode windings on the outer legs or may consist of two separate reactors as shown in this embodiment. The anode windings 22a and 22a of the reactors 22, 22' are respectively connected in serieswith the rectifiers 27, 28 toimpress an alternating current across the rectifier 23. The

on ns n s n ts'fisass e419. v quartet.

circuit "10 ihi ough a lhn'iting-"resistor and vary the flux of the reactors and the output control signal in accordance r th-th m re sat i dstage r output; of the; first; stage through a limiting resistor, and ri t e u he. r ctor; nd. the; o tput o nal inaegordanee. .withthe signal reeeived frorn the first,

ta as.; ind -i a 5. pos ons. efi x oi e terz o he Pr p r. ue-

the transformerfid. v Thebridge rectifier Zfijsconnected in series with theanode, windingJSq, 254:1 across the, sec ondary v of a the transtormer 34. The, output of the. rectiis ;connected to=the ring; modulator l d-through the. filter 36. The,control w inding 25d is coupled across the.

rectifier 23. to receive the amplified input signal,

The anode windings 22a, 2Za,-and the,.,first stage .out-

putrectifier 23 are connected across a portion of the. secondary of'the ttransformer 34. The .feedback winding 22f is connected acrossthe output condenser. Malo-v feed .bacl ;a portion ofthe output. This increases the linearity and accuracy oflthe response of theamplifier. A bias circuit 29,-provides-the bias windings with a direct current to set thefirst and second stage amplifiers in.

their proper operating range. The bias circuit comprises a full wave bridge rectifier 31 supplied with alternatingv current through thetransforrnerv 32.1 The windings. .2211 and 22b and 25b are.connected in parallel across the output filter 33;

This .auxiliary bias .-supply circuit 29Wcomprisesa sup.-v

ply transformer 32 with a secondary .fced bridge rectifier 31, thedirect-current output. of which is filtered bythe L section, chokeinput, filter 33.. The auxiliary bias sup-. ply circuit provides. thebiaswindingsoi the amplifier with the. direct current toposition. the. first and second stage output currents to their proper operating level when zero signal is present. A feedback circuit connects the output of. the secondstage to the feedback winding 22F, 22F" ofthefirst stagethrough a limiting resistor. This circuit feeds backza portion of theoutput of the amplifier in aQnegative manner toeincrease the linearity and accuracy of response of the amplifier.

Thev output signal of the amplifier follows the inputsignal and varies between a maximum and minimumvalue connected=across one. diagonal and the reference circuit connected across theother diagonal. The output signals aretakenfrom-across the resistors 39 and 40 connectedbetween terminals 43, 44 and 42, 45 respectively.

The ring demodulator mixes the two inputvoltages in sucha manner thattheinputsadd in resistors 38- and-41- and-subtract in resistors 39 and 40 since it is desired to subtractthe reference. from the signal subtractings. Resistrs39 and .40.co1nprise.the load of the circuit. These will cart-yea .direct. .current which is porportional to the signal;

The output ot ;the direct referencccircuit-is set by the adjustablemesistorSl to..a .valueto-cahciel the efie ct oi the alternatingreference voltage-impressedon the pri mary windingtl9a of.the.inputtransformere Theoutput- .Q r-z ima brea hs ShilUYPQ? i use 1 54 .5. c nne ted in eri s n; n athli pressa lteru t ne urent cre he-1 c ifie he; i e urr nt: u pu of h ch; 5.. 9. control winding of; the reactor 2g iscoupled across the Anode-.- wi iugs.22a, 24 and 25a, 25a are supplied with alternating current through waslisstqi z usrgtsat ssntst. 5% s... easi y satelliteoutput will be proportional to the .magnitudeof the signal from. the. signal emit 11: and w-ill "be positive or negative in resp onse to thephase of.the signal with respect to the alternating reference voltage.

The direct voljtage reference circuitcomprises a full Wave bridge rectifier 49 and an input transformer 50 connecting rectifier 50 to the source 12. The rectifier is connected, to the adjustable resistor,.51 through the. filter networkdfi and provides; a, direct :voltage larger than. the

direct reference voltage; The -tap 51a is-adjustedto provide thev desired reference. voltage.-

Load circuits can berconnectedto eitheror both resistors. 39; and;40. High impedance-loadsmay .beconnected across theresistors. Low impedance loads may be. connected in-serieswith the loadresistors provided the value v of resistance included between-the junction points 43, 44.

and; 42,. 45 are. kept equal or-in the proper proportions. The load circuitmaybe. any type. of controlled device responsive to a-;direct voltage of reversible polaritysuch as an electricmotor, polarized. relay, electronic circuitor;cont rol.coil-.

Various m ifications and;changes.may be madel in the circl il Withoutrdeparting.frornthe; scopeof the invention,-. The ring rnodulator may have a rectifier-and three resistors instead of four resistors orineachdeg, a reetifier andfiltencircuit instead of resistors-in each leg may be preferred fonbetteraccuracy of response.

I claimg. 1.; An electric conversion. circuit comprising means for comparing an alternating control signal. varied in ampli-.

tude and -reversed in phase. with an alternating reference.

signal hayingan amplitudeslightly-greater than the maximum; amplitude ofisaid signal. to producea direct signal varyingbetweena .magrirnum. and minimum voltage of the same polarity, single-ended amplifying,- means connected to said first means for amplifying said signal, means for combining the-nulput signal of said amplifier and a directs reference. voltage ,having a value to cancel the-efiect of said alternating reference voltage so that the output signal. of;said'circuitis-proportional to said alternating control. signal. anda polarity corresponding e pha eotsaidcon ro gn 2, An electrical circuit comprising a reference source providing ;.an alternating refeliencehsignal, a control circuitconnected=to saidisource .to produceasignal having.

aphasesshi ft-and amplitude.difierencein relationto said.

alternating reference .signal, an. input circuit connected to said source and said'control circuit for combining the signal fromsaid control circuit and the signal from said sour e tq. produce a direct current variable between .a min urn value and-amaximum value-of the same polarity, a single en ded; rnagnetic. amplifiercircuit connected tosaid input circuit-for amplifying said direct current and passing currentpf; only one polarity, .a second, reference circuit havings. constant ,direct voltage having a value to cancel the efiect of ;said,alternating reference signal, a ring modulator; connectedto the output or" said amplifier circuit to; combine the. currents from each circuit to produge a direct; current reversing in polarity on reversal of ;ph ase ot .the alternating signal and; having. a value o erfi nalto theamplitudeot the Signal.

3.; An -,elect-ri,cal-, circuit. comprising a .reference source providingamalternatingsignal, a control circuit connected to saidsourceaosproduce a-signalhaving a phase-shift.

and am plitude-difierence-inrelation-to said 'alternating signal, an input circuit having rectifier and a transformer with two primary windings connected to said source and said control circuit and a secondary winding connected to said rectifier to convert said control circuit signal into a direct signal variable between a minimum value and a maximum value of the same polarity, a single ended amplifier circuit for passing current of one polarity and connected to said input circuit for amplifying said direct current, a second reference circuit having a constant direct voltage having a value to cancel the effect of said alternating reference signal, a ring modulator connected to the output of said amplifier circuit to combine the currents from each circuit to produce a direct current reversing in polarity on reversal of phase of the signal and having a value proportional to the amplitude of the signal.

4. An electrical circuit comprising a reference source providing an alternating signal, a control circuit connected to said source to produce a signal having a phase shift and an amplitude different in relation to said alternating signal, an input circuit connected to said source and said control circuit for the signal current from said control circuit and the signal from said source to produce a direct current variable between a minimum value and a maximum value of the same polarity, a single ended amplifier circuit connected to said input circuit for amplifying said direct current, a second reference circuit having a constant direct voltage having a value to cancel the effect of said alternating reference signal, a ring modulator with four elements connected in a bridge arrangement with the output of the amplifier connected across one diagonal and the output of the reference circuit connected across the other diagonal to produce a voltage across one of said elements reversing in polarity on reversal in phase of the alternating control signal and having a value proportional to the amplitude of the control signal.

5. An electrical circuit adapted to be connected to a source producing an alternating current reference signal having a constant amplitude comprising a control circuit for producing a signal of the same frequency as said reference signal and having a phase shift and an amplitude less than said reference signal conversion. means adapted to be connected to said source to receive said reference signal and connected to said control circuit to receive said control signal for combining said reference signal and said control signal to produce a direct signal variable between a minimum value and a maximum value of the same polarity, single ended amplifier means passing current of only one polarity and connected to said conversion means for amplifying said direct single polarity signal, a reference circuit adapted to produce a direct voltage having a value to cancel the effect of said alternating reference signal, means for combining said direct signal with said direct voltage to produce a direct output current reversing in polarity on reversal of phase of said control signal and having a value proportional to the amplitude of the control signal.

References Cited in the file of this patent UNITED STATES PATENTS 2,021,099 Fitz Gerald Nov. 12, 1935 2,129,920 Fitz Gerald Sept. 13, 1938 2,400,571 Olesen May 21, 1946 2,421,420 Hathaway June 3, 1947 2,478,363 Boosey Aug. 9, 1949 FOREIGN PATENTS 466,874 Canada July 25, 1950 

